Well, I'd say having great conviction and loyalty to your values and being able to withstand resistance and maintain those values no matter what happens. Faith , love, and strength go hand in hand in my view, and that is what makes a strong heart stronger.

While there could be many attributes of a strong heart, the most important aspect of it for me is being able to live the fullness of life amidst all the trials, obstacles and challenges surrounding it. This point of view has been apparent in the persona of Sarah. A virtue that is indeed worth emulating.

" Desire is the starting point of all achievement, not a hope, not a wish but a keen pulsating desire which transcends everything." - Napoleon Hill

She was named Strong Heart because of her conviction. Despite all odds, physical hurt, and internal turmoil, the protagonist did not fail in her endeavour, be it paddling the boat, adjusting to new people, or reading thoughts. Her thin frame did not define her ability, and she proved it by working harder than ever. The character of Strong Heart is quite similar yet unlike Sarah.